The study of peripheral arterial disease in the diabetic has been initiated. The following measurements are being carried out: systolic blood pressure in the upper and lower extremities with transcutaneous Doppler techniques at rest and after exercise; measurement of pulse volume of the extremities by segmental plethesmography and Doppler examination of the arteries; fasting plasma glucose; serum cholesterol and triglycerides; quantitative lipoproteins; platelet factor 4; circulating platelet factor 4: circulating platelet aggregates; platelet aggregation studies, ristocetin Willebrand factor and Willebrand antigen. Clinical data are being abstracted on all subjects recruited. These clinical data include age, sex, height, weight, pertinent history and physical findings and previous laboratory data. A total of 650 study subjects are to be enrolled: 100 normal control subjects, 150 patients with occlusive arterial disease of the lower extremities without diabetes, and 400 diabetic patients with and without occlusive arterial disease of the lower extremities. To date (May 23, 1977), 276 study subjects have been enrolled and their clinical data abstracted. This study will provide data as to the natural history of the progression of vascular disease in diabetic patients and whether it can be correlated with plasma glucose, serum lipids, and more importantly, platelet and plasma coagulation factors. The possible correlation of vascular changes with platelet and plasma factors is an important consideration in the arteriosclerotic disease of diabetic patients. If such a correlation exists, it may provide a mechanism for the development of atherosclerotic lesions in the diabetic and may point to the need for new modes of therapy.